Comparison using neutron diffraction of martensitic transformation in Fe–Mn–Si shape memory alloys with and without VN precipitates

Abstract

Neutron diffraction studies have been performed in situ during thermomechanical testing to quantify the effect of VN precipitates on the development of martensitic transformation, internal stress and texture in Fe–Mn–Si shape memory alloy. To this end, the behaviour of the alloy with and without the addition of VN precipitates has been compared and contrasted. The precipitates promote increased martensitic transformation, while pronouncing differences in extent of transformation between differently oriented austenite grains, leading to increased intergranular stresses. The role of back stress due to Orowan loop formation on the behaviour of the VN bearing material is examined, supported by additional evidence from cyclic tensile and strain recovery tests.